分类： 农、林、牧、渔 >> 农业基础学科 提交时间： 2023-03-19 合作期刊: 《干旱区科学》
摘要：Soil organic carbon (SOC) and its stable isotope composition reflect key information about the carbon cycle in ecosystems. Studies of carbon fractions in oasis continuous cotton-cropped fields can elucidate the SOC stability mechanism under the action of the human-land relationship during the oasification of arid land, which is critical for understanding the carbon dynamics of terrestrial ecosystems in arid lands under global climate change. In this study, we investigated the Alar Reclamation Area on the northern edge of the Tarim Basin, Xinjiang Uygur Autonomous Region of China, in 2020. In original desert and oasis farmlands with different reclamation years, including 6, 10, 18, and 30 a, and different soil depths (0–20, 20–40, 40–60 cm), we analyzed the variations in SOC, very liable carbon (CVL), liable carbon (CL), less liable carbon (CLL), and non-liable carbon (CNL) using the method of spatial series. The differences in the stable carbon isotope ratio (δ13C) and beta (β) values reflecting the organic carbon decomposition rate were also determined during oasification. Through redundancy analysis, we derived and discussed the relationships among SOC, carbon fractions, δ13C, and other soil physicochemical properties, such as the soil water content (SWC), bulk density (BD), pH, total salt (TS), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). The results showed that there were significant differences in SOC and carbon fractions of oasis farmlands with different reclamation years, and the highest SOC was observed at the oasis farmland with 30-a reclamation year. CVL, CL, CLL, and CNL showed significant changes among oasis farmlands with different reclamation years, and CVL had the largest variation range (0.40–4.92 g/kg) and accounted for the largest proportion in the organic carbon pool. The proportion of CNL in the organic carbon pool of the topsoil (0–20 cm) gradually increased. δ13C varied from –25.61‰ to –22.58‰, with the topsoil showing the most positive value at the oasis farmland with 10-a reclamation year; while the β value was the lowest at the oasis farmland with 6-a reclamation year and then increased significantly. Based on the redundancy analysis results, the soil physicochemical properties, such as TN, AP, AK, and pH, were significantly correlated with CL, and TN and AP were positively correlated with CVL. However, δ13C was not significantly influenced by soil physicochemical properties. Our analysis advances the understanding of SOC dynamics during oasification, revealing the risk of soil carbon loss and its contribution to terrestrial carbon accumulation in arid lands, which could be useful for the sustainable development of regional carbon resources and ecological protection in arid ecosystem.
分类： 地球科学 >> 地理学 提交时间： 2021-11-11 合作期刊: 《干旱区科学》
摘要： Land use/cover change (LUCC) is becoming more and more frequent and extensive as a result of human activities, and is expected to have a major impact on human welfare by altering ecosystem service value (ESV). In this study, we utilized remote sensing images and statistical data to explore the spatial-temporal changes of land use/cover types and ESV in the northern slope economic belt of the Tianshan Mountains in Xinjiang Uygur Autonomous Region, China from 1975 to 2018. During the study period, LUCC in the study region varied significantly. Except grassland and unused land, all the other land use/cover types (cultivated land, forestland, waterbody, and construction land) increased in areas. From 1975 to 2018, the spatial-temporal variations in ESV were also pronounced. The total ESV decreased by 4.00×108 CNY, which was primarily due to the reductions in the areas of grassland and unused land. Waterbody had a much higher ESV than the other land use/cover types. Ultimately, understanding the impact of LUCC on ESV and the interactions among ESV of different land use/cover types will help improve existing land use policies and provide scientific basis for developing new conservation strategies for ecologically fragile areas.
分类： 地球科学 >> 地球科学史 提交时间： 2020-06-22 合作期刊: 《干旱区科学》
摘要： Changes in ecological stoichiometry reflect nitrogen (N), phosphorus (P) and both N and P limitations in a plant community, which in turn affect plant diversity of the community. However, the relationship between plant community diversity and ecological stoichiometry has not yet been fully researched in arid and semi-arid regions. Ecological stoichiometry and plant community diversity indices of eighteen communities in the upper reaches of Tarim River, northwestern China, were analyzed by multivariate analysis of variance in 2016. The correlation between ecological stoichiometry and plant community diversity was assessed by redundancy analysis (RDA). Results indicated that the Margalef index was significantly correlated with carbon (C) and P concentrations, the Simpson index and Shannon–Weaner index were significantly correlated with plant C concentration, and the Pielou index was significantly correlated with plant C and N concentrations. Moreover, C:N and C:P ratios had significant impacts on plant community diversity. Our results highlight the importance of ecological stoichiometry in driving plant community diversity in the upper reaches of Tarim River, northwestern China.
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